1. Technical Field
Photo-fabrication processing is widely used as a micro-precision processing method necessary in the manufacture and formation of IC lead frames, color television shadow masks, high density printed circuit boards, miniature gears and the electrodes and partitions in thin displays (LCD-PDP). The present invention relates to a photomask plate having a film surface protective layer used in this type of photo-fabrication processing. The present invention further relates to a method of manufacturing such a photomask plate having a film surface protective layer. Additionally, the present invention relates to a solution for forming a film surface protective layer used in this type of photo-fabrication processing.
In the aforementioned photo-fabrication processing, the surface to be treated is covered with a corrosion resistant film, which is then partially removed.
Next, photo-etching methods are used to chemically dissolve and remove the exposed surface. Optionally, photo-electroforming methods are used to grow a metal by electroforming.
In both of these methods, the portions of the surface which are not to be processed are covered with a corrosion resistant film, so that the processing is performed subsequent to a masking process. The masking process is typically a photographic method in which a precision made photographic image is superimposed on a photomask made of a photosensitive material which has photosensitivity to ultraviolet light. The photomask is then exposed, developed and dried. Almost all of the photomask plates used in this type of photographic method are emulsion photomasks, formed by adhering a photosensitive emulsion layer in a film state, comprising gelatin or the like as the main constituent, to the surface of a substrate.
The present invention relates to technology for forming a film surface protective layer for protecting a photomask, and in particular an emulsion photomask, of a photomask plate. 2. Background Art
Conventional photomask plates are manufactured using a CAD system, or the like, to prepare data for an exposure apparatus (such as a photo-plotter) based on a target blueprint or data Then, this data is used to perform direct writing of a pattern onto an emulsion photographic dry plate. Finally, the photographic dry plate with the pattern drawn thereon is developed, fixed, washed in water, dried, retouched, and examined.
A conventional photomask plate emulsion photomask (a film surface of a photosensitive emulsion layer), formed in this manner, comprises gelatin or the like as the main constituent. Thus, the film surface is soft and easily marked. Furthermore, other problems also exist. For example, if soiling, such as that resulting from a fingerprint, adheres to the film surface of the photomask, then subsequent removal of the soiling is difficult.
A first method of resolving this problem involves laminating an approximately 8xcexcxcx9c12xcexc film as a protective film onto the film surface of the photomask. However, this laminated protective film method suffers from poor sensitivity, as passage through the protective film reduces the transmittance of the ultraviolet light to approximately 50%.
A second method involves replacing the photosensitive emulsion film (emulsion photomask) with a metal film containing chromium (Cr900A) which is formed in a pattern on the surface of a glass substrate (a chrome mask) as the photomask. Chrome masks, however, are extremely expensive (between four and five times the cost of an emulsion photomask) and, consequently, suffer from being somewhat impractical.
It is an object of the present invention to provide a photomask which overcomes the foregoing problems.
It is an object of the present invention is to provide a cheap and durable photomask, by forming a second protective layer on top of an emulsion photomask produced by conventional methods. This object of the present invention overcomes the problems of the photomask being easily marked or easily soiled. Moreover, reductions in ultraviolet light transmittance, such as those observed for laminated protective films, are prevented.
Briefly stated, the present invention provides a photomask plate with a film surface protective layer characterized in that a protective layer forming solution is prepared by mixing a main constituent comprising a two-liquid cross-linked antifouling surface coating agent, prepared by combining a mixed resin of a fluororesin and an acrylic resin in a solvent mixture of n-butyl acetate, methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK), with a cross-linking curing agent, prepared by mixing a polyisocyanate prepolymer and ethyl acetate, and a diluent comprising n-butyl acetate, methyl ethyl ketone (MEK) and cellosolve (ethylene glycol monoethyl ether) acetate. This protective layer forming solution is applied to a film surface of a photomask plate photosensitive emulsion layer produced by forming the film surface of the photosensitive emulsion layer (an emulsion photomask) on a substrate. The protective layer forming solution is then aged to form a film surface protective layer in a laminated manner. The resulting inexpensive and durable photomask is protected from being soiled or marked while having minimal reduction in ultraviolet light transmittance.
According to a first embodiment of the present invention, there is provided a photomask plate with a film surface protective layer, wherein a protective layer forming solution prepared by combining and mixing a mixed resin solution, comprising a fluororesin and an acrylic resin as the main constituents, and a mixed solution, comprising a polyisocyanate prepolymer as the main constituent, is applied to a film surface of a photomask plate photosensitive emulsion layer produced by forming the film surface of the photosensitive emulsion layer (an emulsion photomask) on a substrate. The protective layer forming solution is then aged to form a two-liquid cross-linked film surface protective layer in a laminated manner.
This first embodiment of the present invention is characterized by the formation of a two-liquid cross-linked film surface protective layer as a second layer on the surface of a typical photomask plate produced by forming a photosensitive emulsion layer (an emulsion photomask) on a substrate. The two-liquid cross-linked film surface protective layer is a two-liquid cross-linked synthetic resin film surface protective layer produced by chemical curing when a mixed resin solution, comprising a fluororesin and an acrylic resin, and a mixed solution, comprising a polyisocyanate prepolymer as the main constituent, are mixed together and then aged. The film surface protective layer displays excellent adhesion, forms a highly durable coating on a wide variety of soft and hard materials including acrylic resins, vinyl chloride, urethane resins and glass, is a colorless and transparent liquid, displays little tendency to whiten under bending or stretching, and produces almost no reduction in the transmittance of ultraviolet light. These properties make the film surface protective layer ideal for protecting a photomask plate.
According to a second embodiment of the present invention there is provided a photomask plate with a film surface protective layer, wherein a protective layer forming solution is prepared by mixing a main constituent, comprising a two-liquid cross-linked antifouling surface coating agent prepared by combining a mixed resin of a fluororesin and an acrylic resin in a solvent mixture of n-butyl acetate, methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK), with a cross-linking curing agent, prepared by mixing a polyisocyanate prepolymer and ethyl acetate, and a diluent comprising n-butyl acetate, methyl ethyl ketone (MEK) and cellosolve (ethylene glycol monoethyl ether) acetate. The resulting protective layer forming solution is applied to a film surface of a photomask plate photosensitive emulsion layer produced by forming the film surface of the photosensitive emulsion layer (an emulsion photomask) on a substrate. The protective layer forming solution is then aged to form a film surface protective layer in a laminated manner.
This second embodiment of the present invention includes a photomask plate with a film surface protective layer in which a two-liquid cross-linked antifouling surface coating agent (a main constituent) and a cross-linking curing agent are each dissolved in a predetermined solvent. These two solutions, together with a diluent which is added to enable the two solutions to be diluted as required and applied as a thin film as well as enable easier control of the rate of chemical change, generate a new photomask protective layer forming solution. This protective layer forming solution is applied and then aged to form a practical film surface protective layer. In other words, the second embodiment of the present invention is characterized by the formation, on a photosensitive emulsion layer of a conventional photomask plate, of a film surface protective layer as a second layer by application of a protective layer forming solution, where the film surface protective layer improves the durability of the photomask with very little loss of functionality thereof. The two-liquid cross-linked antifouling surface coating agent, which is the main constituent of the film surface protective layer forming solution, is a two-liquid cross linked type surface coating agent with excellent adhesion properties, which is produced by forming a resin solution of a fluororesin and an acrylic resin dissolved in a solvent, and which forms a highly durable coating on a wide variety of soft and hard materials including acrylic resins, vinyl chloride, urethane resins and glass, and is a colorless and transparent liquid which displays little tendency to whiten under bending or stretching, and produces almost no reduction in the transmittance of ultraviolet light.
Furthermore, the cross-linking curing agent is a mixed solution prepared by dissolving a polyisocyanate prepolymer (structural formula: a trimethylolpropane adduct of hexamethylene diisocyanate) in a solvent. The cross-linking curing agent displays good transparency, and, when mixed with the main constituent, undergoes a reaction to generate cross-linking while curing to form a highly transparent film.
The aforementioned protective layer forming solution is a mixture of a main constituent, comprising a two-liquid cross-linked surface coating agent, prepared by dissolving the aforementioned resin mixture in a solvent to form a resin solution, to which a cross-linking curing agent and a diluent are added. None of the used solvent or diluent will remain by the completion of the aging process. Thus, the two-liquid cross-linked film surface protective layer formed will display the properties of the main constituent and the cross-linking curing agent. Consequently, a photomask plate with a film surface protective layer according to the present invention will be a low cost yet durable photomask which is not easily marked or soiled, and which does not reduce the transmittance of ultraviolet light.
According to a third embodiment of the present invention, there is provided a photomask plate with a film surface protective layer, wherein a protective layer forming solution is prepared by mixing 25xcx9c50% of a main constituent, comprising a two-liquid cross-linked antifouling surface coating agent prepared by combining a mixed resin of a fluororesin and an acrylic resin in a solvent mixture of n-butyl acetate, methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK), with 1xcx9c6% of a cross-linking curing agent, prepared by mixing a polyisocyanate prepolymer and ethyl acetate, and 46xcx9c75% of a diluent comprising n-butyl acetate, methyl ethyl ketone (MEK) and cellosolve (ethylene glycol monoethyl ether) acetate. The resulting protective layer forming solution is applied to a film surface of a photomask plate photosensitive emulsion layer produced by forming the film surface of an emulsion layer (an emulsion photomask) on a substrate. The protective layer forming solution is then chemically altered to form a film surface protective layer.
According to a feature of this third embodiment of the present invention, by specifying the respective proportions in the mixture of the main constituent, the cross-linking curing agent and the diluent which constitute the protective layer forming solution, enables the implementation of a more favorable photomask plate with a film surface protective layer.
According to a fourth embodiment of the present invention, there is provided a photomask plate with a film surface protective layer according to either the second or the third embodiments, above, wherein the two-liquid cross- linked antifouling surface coating agent, as the main constituent of the protective layer forming solution, is a mixed resin solution comprising a mixed resin of 5xcx9c20% of a fluororesin and 10xcx9c30% of an acrylic resin in a solvent mixture comprising 20xcx9c30% n-butyl acetate, 30xcx9c40% methyl ethyl ketone (MEK) and 5xcx9c10% methyl isobutyl ketone (MIBK). The cross-linking curing agent is a mixed solution comprising 70xcx9c80% of a polyisocyanate prepolymer and 20xcx9c30% ethyl acetate, and the diluent is a mixed solution comprising 10xcx9c20% n-butyl acetate, 50xcx9c60% methyl ethyl ketone (MEK) and 25xcx9c40% cellosolve (ethylene glycol monoethyl ether) acetate.
This fourth embodiment of the present invention specifies the respective proportions of the main constituent, the cross-linking curing agent and the diluent which constitute the protective layer forming solution, as well as the proportions of the materials which are mixed to produce the above constituents. This enables the implementation of a more favorable photomask plate with a film surface protective layer.
According to a fifth embodiment of the present invention, there is provided a method of manufacturing a photomask plate with a film surface protective layer, wherein a protective layer forming solution is prepared by mixing a main constituent, comprising a two-liquid cross-linked antifouling surface coating agent prepared by combining a mixed resin of a fluororesin and an acrylic resin in a solvent mixture of n-butyl acetate, methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK), with a cross-linking curing agent, prepared by mixing a polyisocyanate prepolymer and ethyl acetate, and a diluent comprising n-butyl acetate, methyl ethyl ketone (MEK) and cellosolve (ethylene glycol monoethyl ether) acetate. The protective layer forming solution is applied using an application method such as dip coating, spin coating, roll coating or spray coating to a film surface of a photomask plate photosensitive emulsion layer, which is produced by preparing an emulsion photographic dry plate by forming a film surface of a photosensitive emulsion layer (an emulsion photomask) on a substrate. A pattern is rendered and development treatment, such as developing, fixing, washing in water, and drying, is performed. Finally, the film surface is inspected and retouched, and the protective layer forming solution is then aged to form a film surface protective layer.
The fifth embodiment of the present invention is a method of manufacturing a photomask plate with a film surface protective layer. By application of a predetermined protective layer forming solution onto a prepared photomask plate, and subsequent aging, a film surface protective layer is formed through chemical change and drying. A variety of methods of application are available such as spray coating, spin coating, dip coating or roll coating, and any of these methods is suitable. However, from a practical viewpoint, in order to form a uniform film of only several microns in thickness, the use of spray coating is preferable. A method of manufacturing a photomask plate with a film surface protective layer, according to the present invention, includes preparing and uniformly applying a suitable protective layer forming solution. As a result, the surface quality of the film is good and a thin film surface protective layer is generated naturally. Thus, operations such as final polishing treatment are unnecessary, and consequently the manufacturing process is simplified.
According to a sixth embodiment of the present invention, there is provided a protective layer forming solution for a photomask plate, wherein a main constituent comprising a two-liquid cross-linked antifouling surface coating agent, prepared by combining a mixed resin of a fluororesin and an acrylic resin in a solvent mixture of n-butyl acetate, methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK), is combined and mixed with a cross-linking curing agent, prepared by mixing a polyisocyanate prepolymer and ethyl acetate, and a diluent comprising n-butyl acetate, methyl ethyl ketone (MEK) and cellosolve (ethylene glycol monoethyl ether) acetate.
According to a seventh embodiment of the present invention, there is provided a protective layer forming solution for a photomask plate in which a main constituent two-liquid cross-linked antifouling surface coating agent is a mixed resin solution formed by combining a mixed resin of 5xcx9c20% of a fluororesin and 10xcx9c30% of an acrylic resin with a solvent mixture comprising 20xcx9c30% n-butyl acetate, 30xcx9c40% methyl ethyl ketone (MEK) and 5xcx9c10% methyl isobutyl ketone (MIBK). A cross-linking curing agent is a mixed solution comprising 70xcx9c80% of a polyisocyanate prepolymer and 20xcx9c30% ethyl acetate, and a diluent is a mixed solution comprising 10xcx9c20% n-butyl acetate, 50xcx9c60% methyl ethyl ketone (MEK) and 25xcx9c40% cellosolve (ethylene glycol monoethyl ether) acetate. These constituents are combined and mixed in a ratio of 25xcx9c50% of the main constituent, 1xcx9c6% of the cross-linking curing agent, and 46xcx9c75% of the diluent.
A feature of the seventh embodiment of the present invention specifies in more detail the components of the main constituent, the cross-linking curing agent and the diluent which constitute the protective layer forming solution, as well as the respective proportions of each of the materials incorporated therein. This enables the implementation of a more favorable photomask plate with a film surface protective layer.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawing, in which like reference numerals designate the same elements.